First HDR video system shows all the light and shade


Glaring, overlit faces and blacked-out night-time backgrounds have ruined photographs, film and video ever since they were invented. Why can't cameras just record things the way our eyes see them? Now a video system based on new data-crunching techniques means they can. New Scientist explores what it will mean for the picture on your TV screen.The dynamic range of an image is the difference in brightness between the lightest and darkest areas of the scene. Our eyes can handle a much wider range of brightnesses than conventional cameras and can adjust to sudden changes in light much more quickly. That's why cameras often give under- or over-exposed images of scenes that were perfectly clear to the naked eye. HDR cameras get around this problem by taking a number of pictures at different exposures and combine them to give a more realistic depiction of a scene.

"HDR is what we see every day of our lives," explains Alan Chalmers at the University of Warwick, UK, who worked on the new camera system.The idea of combining images made at different exposure levels to enhance the realism of still photographs dates back to the 1850s, but it's only in the past decade that it has really taken off, as photographers use the internet to display their work and swap techniques. Check out the HDR pool on Flickr for a half-million or so examples.

These photos were made using software to combine several exposures taken one after another – using a tripod-mounted camera to make sure that the outlines of the images match. Many modern stills cameras such as the Canon EOS 5D include settings to automatically adjust the exposure, and the Apple iPhone 4 will capture three still images and combine them automatically to maximise dynamic range.Capturing HDR video involves continuously recording a scene at multiple exposure levels, a difficult technological challenge. Last September San Francisco-based studio Soviet Montage created an HDR video (see video above) using a beam splitter that sent light from one scene to two EOS 5D Mk II cameras – which can record HD video – one of which was underexposed, the other overexposed. High-end movie camera manufacturer Red is also working on HDR video.

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